Liners have been commonly used in the past for sealing between a bottle or other like container having an opening and a cap securable to the bottle for enclosing the opening. A fluid impervious seal at the bottle opening is highly desirable to preclude permeation or leakage of fluids into and/or out of the bottle. For the purposes of this application, "permeation" means the passage of a fluid directly through a barrier, such as a cap liner, by absorbing or adsorbing into the barrier at a high concentration side, diffusion through the material of the barrier in the direction of the side of lower concentration, and then desorbing from the barrier on the low concentration side. The term "leakage" on the other hand, means the passage of fluid through a gap between a barrier and an object such as a cap liner and a bottle.
Conventional cap liners have included one piece liners constructed of a material such as corrugated fiberboard, paperboard or the like, and may also include a coating on one or both major surfaces that is resistant to fluid permeation. However, such designs, although relatively inexpensive, are not flexible, durable, structurally strong, or completely effective in precluding permeation or leakage of fluids into or out of a bottle. Further, corrugated fiberboard or paperboard liners generate undesirable quantities of dust or other particulates that may contaminate the contents of the bottle.
Cap liners have been constructed of synthetic materials such as thermoplastics. U.S. Pat. No. 4,121,728 entitled "Venting Liners" and issued to Tagalakis, shows one such cap liner having a first ply constructed of an impermeable plastic and a second ply constructed of a foamed material that is compressibly deformable. Both plys are simultaneously extruded and laminated together to form the cap liner. The first ply of the cap liner is applied to the bottle as the cap is secured to the bottle. The second ply is compressed between the bottle and the cap and urges the first ply into sealing contact with the bottle.
Although cap liners such as in the Tagalakis patent are more effective than cardboard cap liners against fluid permeation or leakage, such cap liners inherently require relatively expensive materials and manufacturing techniques. For example, the second ply in the Tagalakis patent provides an imperforate and coextensive layer of deformable material, even though only a relatively small portion of the second ply is actually compressed between the bottle and the cap. The remainder of the second ply is not required to mechanically reinforce the first ply. Therefore, the non-essential material in the second ply represents an unnecessary expense.